Touch display apparatus sensing touch force

ABSTRACT

A touch display device is provided which includes a display panel for displaying an image, and a touch screen panel disposed on the display panel and configured to sense at least one touch. The touch screen panel includes a touch substrate at which the touch can be generated; sensing electrodes provided on the touch substrate and spaced apart from one another, each of the sensing electrodes being formed of a piezoresistive material having a resistance value that varies according to an applied force; and a touch processor electrically connected to the sensing electrodes. The touch processor extracts a touch coordinate based on time constants of sensing signals applied to the sensing electrodes, and calculates a touch force of the touch based on resistance values of the sensing electrodes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation application of U.S. patentapplication Ser. No. 13/763,451, filed on Feb. 8, 2013, which claims thebenefit under 35 U.S.C. §119(a) of Korean Patent Application No.10-2012-0092916, filed on Aug. 24, 2012 in the Korean IntellectualProperty Office, the entire contents of which are hereby incorporated byreference.

BACKGROUND

Embodiments of the present invention relate generally to touch displaydevices. More particularly, embodiments of the present invention relateto touch display devices capable of sensing a touch force using apiezoresistive material.

Functions of information display devices such as cellular phones, PDAs,navigation systems, etc. may be expanded into multimedia providingfields. Conventional information display devices may use key pads asinput means. Recent information display devices employ a touch screenpanel as input means to forego a keyboard and provide a larger displayscreen. A touch screen panel may be attached to the display panel of aninformation display device.

While a conventional touch screen panel senses the location of a touchinput by a user, it may not sense a force applied by the user. Theconventional touch screen panel may require a separate force sensor forsensing a force applied by the user. This may cause an increase in aproduction cost.

SUMMARY

A touch display device according to an embodiment of the inventiveconcept comprises a display panel, and a touch screen panel disposed onthe display panel and configured to sense at least one touch. The touchscreen panel comprises a touch substrate, sensing electrodes, and atouch processor.

The touch substrate can be formed of a flexible insulation material.

The sensing electrodes are provided on the touch substrate to be spacedapart from one another, and each of the sensing electrodes can comprisea piezoresistive material having a resistance that varies according toan applied force. The piezoresistive material can be carbon nanotube(CNT) or graphene.

The touch processor is electrically connected to the sensing electrodes.The touch processor can be configured to extract a touch coordinate ofthe touch based on time constants of sensing signals applied to thesensing electrodes, and to calculate a touch force of the touch based onresistance values of the sensing electrodes.

The touch processor can comprise a signal providing unit configured toprovide the sensing signals to the sensing electrodes; and a signalprocessing unit configured to determine the time constants of thesensing signals so as to facilitate output of the touch coordinate andthe touch force.

The signal processing unit can comprise a touch determining partconfigured to determine the presence of the touch and to determinewhether the touch is a soft touch or a hard touch, by comparing the timeconstants to a predetermined reference time constant; a coordinateextracting part configured to extract the touch coordinate fromlocations of sensing electrodes whose respective sensing signals havetime constants corresponding to the touch; and a touch force calculatingpart configured to calculate the touch force based on a resistance valueof a sensing electrode corresponding to the touch coordinate.

A touch display device is configured as that according to an embodimentof the inventive concept except for a touch processor. The touchprocessor is electrically connected to the sensing electrodes and isconfigured to extract a touch coordinate and a touch force of the touchbased on resistance values of the sensing electrodes.

The touch processor comprises an electrode resistor providing resistancevalues of the sensing electrodes; a reference resistor connected inseries to the electrode resistor and having a substantially constantresistance value; and a touch determining part connected to a nodebetween the electrode resistor and the reference resistor and configuredto determine the presence of a touch as well as whether the touch is asoft touch or a hard touch based on a division voltage at the node; acoordinate extracting part configured to extract the touch coordinatefrom a location of a sensing electrode corresponding to the divisionvoltage; and a touch force calculating part configured to calculate thetouch force based on a resistance value of a sensing electrodecorresponding to the touch coordinate.

BRIEF DESCRIPTION OF THE FIGURES

The above and other objects and features will become apparent from thefollowing description with reference to the following figures, whereinlike reference numerals refer to like parts throughout the variousfigures unless otherwise specified.

FIG. 1 is a perspective view of a touch display device according to anembodiment of the inventive concept.

FIG. 2 is a cross-sectional view taken along a line IT in FIG. 1.

FIG. 3 is a top view of a touch screen panel.

FIG. 4 is a block diagram schematically illustrating a touch screenpanel.

FIG. 5 is a block diagram schematically illustrating a signal processingunit in FIG. 4.

FIG. 6 is a diagram illustrating a waveform of a sensing signal having areference time constant.

FIG. 7 is a circuit diagram of a touch force calculating unit.

FIG. 8 is a cross-sectional view of a touch display device according toanother embodiment of the inventive concept.

FIG. 9 is a top view of a touch screen panel in FIG. 8.

FIG. 10 is a perspective view of a touch display device according tostill another embodiment of the inventive concept.

FIG. 11 is a diagram illustrating a touch processor according to stillanother embodiment of the inventive concept.

FIG. 12 is a graph illustrating a division voltage according to a touchforce.

DETAILED DESCRIPTION

Embodiments will be described in detail with reference to theaccompanying drawings. The inventive concept, however, may be embodiedin various different forms, and should not be construed as being limitedonly to the illustrated embodiments. Rather, these embodiments areprovided as examples so that this disclosure will be thorough andcomplete, and will fully convey the concept of the inventive concept tothose skilled in the art. Accordingly, known processes, elements, andtechniques are not described with respect to some of the embodiments ofthe inventive concept. Unless otherwise noted, like reference numeralsdenote like elements throughout the attached drawings and writtendescription, and thus descriptions will not be repeated. In thedrawings, the sizes and relative sizes of layers and regions may beexaggerated for clarity.

It will be understood that, although the terms “first”, “second”,“third”, etc., may be used herein to describe various elements,components, regions, layers and/or sections, these elements, components,regions, layers and/or sections should not be limited by these terms.These terms are only used to distinguish one element, component, region,layer or section from another region, layer or section. Thus, a firstelement, component, region, layer or section discussed below could betermed a second element, component, region, layer or section withoutdeparting from the teachings of the inventive concept.

Spatially relative terms, such as “beneath”, “below”, “lower”, “under”,“above”, “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. It will beunderstood that the spatially relative terms are intended to encompassdifferent orientations of the device in use or operation in addition tothe orientation depicted in the figures. For example, if the device inthe figures is turned over, elements described as “below” or “beneath”or “under” other elements or features would then be oriented “above” theother elements or features. Thus, the exemplary terms “below” and“under” can encompass both an orientation of above and below. The devicemay be otherwise oriented (rotated 90 degrees or at other orientations)and the spatially relative descriptors used herein interpretedaccordingly. In addition, it will also be understood that when a layeris referred to as being “between” two layers, it can be the only layerbetween the two layers, or one or more intervening layers may also bepresent.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the inventiveconcept. As used herein, the singular forms “a”, “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises” and/or “comprising,” when used in this specification,specify the presence of stated features, integers, steps, operations,elements, and/or components, but do not preclude the presence oraddition of one or more other features, integers, steps, operations,elements, components, and/or groups thereof. As used herein, the term“and/or” includes any and all combinations of one or more of theassociated listed items. Also, the term “exemplary” is intended to referto an example or illustration.

It will be understood that when an element or layer is referred to asbeing “on”, “connected to”, “coupled to”, or “adjacent to” anotherelement or layer, it can be directly on, connected, coupled, or adjacentto the other element or layer, or intervening elements or layers may bepresent. In contrast, when an element is referred to as being “directlyon,” “directly connected to”, “directly coupled to”, or “immediatelyadjacent to” another element or layer, there are no intervening elementsor layers present.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this inventive concept belongs. Itwill be further understood that terms, such as those defined in commonlyused dictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art and/orthe present specification and will not be interpreted in an idealized oroverly formal sense unless expressly so defined herein.

FIG. 1 is a perspective view of a touch display device according to anembodiment of the inventive concept. FIG. 2 is a cross-sectional viewtaken along a line I-I′ in FIG. 1.

Referring to FIGS. 1 and 2, a touch display device 1000 may include adisplay panel 100 and a touch screen panel 200.

The display panel 100 may display images. The display panel 100 may anytype of display panel, such as a liquid crystal display panel, anorganic light emitting display panel, a plasma display panel, anelectrophoretic display panel, an electro-wetting display panel, and soon.

A shape of the display panel 100 in a plane view (i.e. a view along anormal to the image-displaying face of display panel 100) is notnecessarily limited to any specific shape. In FIGS. 1 and 2, there isillustrated an example in which a shape of the display panel 100 isrectangular in a plane view.

The touch screen panel 200 may include a touch substrate SB, sensingelectrodes SE, and a touch processor (not shown).

The touch substrate SB may be used to sense the touch of a user. Thetouch substrate SB may be formed of a flexible material such as plastic.

The touch substrate SB may have a plate shape. More specifically, thetouch substrate SB may have a platelike shape corresponding to a shapeof the display panel 100. In FIGS. 1 and 2, there is illustrated anexample in which the shape of the touch substrate SB is rectangular in aplane view.

The sensing electrodes SE may be disposed on the touch substrate SB. Thesensing electrodes SE may be spaced apart from one another. In addition,the sensing electrodes SE may have island shape, respectively. Thesensing electrodes SE may be formed of a piezoresistive material, theresistance value of which varies according to a force applied thereto.For example, the piezoresistive material may be carbon nanotube (CNT),graphene, or the like. The carbon nanotube may be Single Walled CarbonNanotubes (SWNT) or Multi Walled Carbon Nanotubes (MWNT). In the casethat the piezoresistive material is pressed, its conductivity maydecrease and its resistance value may increase.

The piezoresistive material may be substantially transparent. Lightincident onto the sensing electrodes SE may largely pass through thesensing electrodes SE. Thus, although the sensing electrodes SE aredisposed to be overlapped with the display panel 100 in a plane view,brightness of an image displayed by the display panel 100 may not besubstantially affected.

The touch screen panel 200 may further comprise a plurality of spacersSP. In FIGS. 1 and 2, there is illustrated an example in which fourspacers SP are disposed at four corners of the touch substrate SB,respectively. However, any number and placement of spacers iscontemplated.

The spacers SP may be disposed between the touch substrate SB and thedisplay panel 100. The spacers SP may perform the role of maintaining acell gap between the touch substrate SB and the display panel 100.

Heights of the spacers SP may be greater than those of the sensingelectrodes SE. Thus, the sensing electrodes SE may be spaced apart fromthe display panel 100 in a height direction. A space between the touchsubstrate SB and the display panel 100 (i.e. the space within which thesensing electrodes SE reside) may be filled by air.

Although not shown in the figures, the touch processor may be mounted onthe touch screen panel 200 as a chip type processor, or may be providedon a printed circuit board connected with the touch screen panel 200.

FIG. 3 is a top view of a touch screen panel. FIG. 4 is a block diagramschematically illustrating a touch screen panel. In FIG. 3, there isillustrated an example in which a touch TCH is made at a touch substrateSB by a user. Herein, the touch TCH may be generated on 21th sensingelectrode SE21 in a plane view, and a touch force F1 corresponding tothe touch TCH may be applied in a direction perpendicular to the touchscreen SB, i.e. into the touch screen panel.

Referring to FIGS. 3 and 4, sensing electrodes SE may be arranged in amatrix of i rows and j columns (i and j being a natural number). In FIG.3, there is illustrated an example in which sensing electrodes SE1 toSE60 are arranged in a matrix of 6 rows and 10 columns. Also, each ofthe sensing electrodes SE1 to SE60 may be rectangular in a plane view.

The touch screen panel 200 may further include touch lines TL1 to TL60provided on the touch substrate SB. The touch lines TL1 to TL60 mayconnect the sensing electrodes SE1 to SE60 to a touch processor CP.

A part of the touch lines connected to sensing electrodes of a kthcolumn (k being a natural number satisfying i≦k<j) may be disposedbetween the sensing electrodes of the kth column and the adjacent(k+1)th column. In FIG. 3, touch lines TL1 to TL10 connected to sensingelectrodes SE1 to SE10 of a first column may be disposed between thesensing electrodes SE1 to SE10 of the first column and sensingelectrodes SE11 to SE20 of a second column. The touch lines TL1 to TL60may be extended in a column direction.

The touch processor CP may include a signal providing unit 300 and asignal processing unit 400.

The signal providing unit 300 may sequentially provide sensing signalsSG to the sensing electrodes SE. The sensing signals SG may be currentsignals or voltage signals. In FIG. 3, there is illustrated an examplein which sensing signals SG1 to SG60 are provided to the sensingelectrodes SE1 to SE60, respectively.

The signal processing unit 400 may sense sensing time constants TS whichare time constants of the sensing signals SG provided to the sensingelectrodes SE (i.e., measures of the amount of time the voltage acrossthe sensing electrode SE takes to reach a certain level). At this time,a sensing time constant of a sensing signal SG21 provided to a sensingelectrode SE21 located at a point where the touch TCH is generated maybe different from a sensing time constant of each of sensing signals SG1to SG20 and SG22 to SG60 located at points where the touch TCH is notgenerated.

In particular, if the touch TCH is generated, a touch capacitor may begenerated between a user and a 21st sensing electrode SE21. Thisgenerated touch capacitor may be connected in parallel with an inherentcapacitor of the 21st sensing electrode SE21. The combined capacitanceof the touch and inherent capacitors may be larger than that of theinherent capacitance, and a sensing time constant of a sensing signalSG21 provided to the 21st sensing electrode SE21 may be greater thanthat when the touch TCH is not generated.

The signal processing unit 400 may extract a touch coordinate of thetouch TCH, and may calculate a touch force of the touch TCH to provideit to the display panel 100.

FIG. 5 is a block diagram schematically illustrating the signalprocessing unit 400 of FIG. 4. FIG. 6 is a diagram illustrating awaveform of a sensing signal having a reference time constant. FIG. 7 isa circuit diagram of a touch force calculating unit. In FIG. 6, asensing signal may be assumed to be a voltage signal.

Referring to FIG. 5, a signal processing unit 400 may include a touchdetermining part 410, a coordinate extracting part 420, and a touchforce calculating part 430.

The touch determining part 410 may determine whether a touch isgenerated and whether the touch is a soft touch or a hard touch. Thismay be determined by comparing a sensing time constant τs to apredetermined reference time constant.

Referring to FIG. 6, the reference time constant may include a firstreference time constant τ1 and a second reference time constant τ2. Thatthe sensing time constant τs is larger than the first time constant τ1may mean that a touch is generated. In the event that the sensing timeconstant τs is larger than the first time constant τ1 and smaller thanthe second time constant τ2, the touch determining part 410 maydetermine the touch be a soft touch. In the event that the sensing timeconstant τs is larger than the second time constant τ2, the touchdetermining part 410 may determine the touch be a hard touch.

Returning to FIG. 5, the touch determining part 410 may provide thedisplay panel 100 with a first control signal CN1 indicating that notouch is generated.

When a touch is generated, the touch determining part 410 may providethe coordinate extracting part 420 with a second control signal CN2including information associated with a soft/hard touch.

The coordinate extracting part 420 may extract the touch coordinate froma location of a sensing electrode corresponding to the sensing timeconstant. That is, the time constants for each sensing electrode aredetermined, and a touch is deemed to have occurred at a particularsensor when its time constant grows greater than τ1 and/or τ2.

Referring to FIGS. 3 and 6, in the case that a sensing time constant τsof a sensing signal SG21 applied to a 21st sensing electrode SE21becomes larger than the first reference time constant τ1, the coordinateextracting part 420 may decide a location of the 21st sensing electrodeSE21 as a touch coordinate.

The coordinate extracting part 420 may provide the display panel 100with a third control signal CN3 including information associated withthe touch coordinate. A display panel illustrated in FIGS. 1 and 2 mayreceive the third control signal CN3 to convert it into an image suchthat information directed by the touch coordinate is displayed. Also,when the touch is a hard touch, the coordinate extracting part 420 mayprovide the third control signal CN3 to the touch force calculating part430.

The touch force calculating part 430 may calculate the touch force basedon a resistance value of a sensing electrode corresponding to the touchcoordinate.

Referring to FIGS. 3 and 7, the touch force calculating part 430 mayinclude an electrode resistor Rs, a reference resistor Rf, and a forcesensing part FSP.

The electrode resistor Rs may have the same resistance value as that ofeach of the sensing electrodes SE1 to SE60. In more detail, theelectrode resistor Rs may be an equivalent resistor of the sensingelectrodes SE1 to SE60 seen from the touch force calculating part 430.That is, resistor Rs is an adjustable resistor whose resistance value isset to the resistance value of the sensing electrode that is receivingthe touch force F1. The resistance value of the piezoresistive elementis determined from the change in its sensing signal due to the touch,and Rs is set accordingly.

Thus, a resistance value of the electrode resistor Rs may vary when aresistance value of the sensing electrodes SE1 to SE60 is varied by thetouch force F1.

The reference resistor Rf may be connected in series with the electroderesistor Rs, and may have a constant resistance value.

The resistors Rf and Rs may be connected in series between a setupvoltage Vcc and a ground. One end of the reference resistor Rf may beconnected to a reference potential Vcc, one end of the electroderesistor Rs may be grounded, and the other ends of the resistors Rf andRs may be connected to each other.

The force sensing part FSP may be connected to a connection node of theresistors Rf and Rs. The force sensing part FSP may sense a divisionvoltage Vd decided by dividing the reference potential Vcc using theresistors Rf and Rs. The division voltage Vd may vary according to avariation in a resistance value of the electrode resistor Rs.

The division voltage Vd may be decided by the following equation 1.

${Vd} = {{Vcc} \times \frac{Rs}{{Rf} + {Rs}}}$

Herein, Vd, Vcc, Rf, and Rs may indicate a division voltage, a referencepotential, a resistance value of a reference resistor, and a resistancevalue of an electrode resistor, respectively.

The force sensing part FSP may calculate the touch force F1 based on thedivision voltage Vd.

For example, in the case that a force is not applied to a 21st sensingelectrode SE21, a resistance value of the electrode resistor Rs may beinfinite. In the case that an infinite force is applied to the 21thsensing electrode SE21, a resistance value of the electrode resistor Rsmay be zero. As a resistance value of the electrode resistor Rs varies,the division voltage Vd may vary between 0V and Vcc.

The force sensing part FSP may include a lookup table including forcevalues respectively corresponding to voltage values between 0V and Vcc.The force sensing part FSP may read a touch force F1 corresponding tothe division voltage Vd from the lookup table. However, the inventiveconcept is not limited thereto. For example, the force sensing part FSPmay be configured to calculate the touch force F1 from the divisionvoltage Vd using an appropriate coefficient.

The touch force calculating part 430 may provide the display panel 100with a fourth control signal CN4 having information associated with thetouch force F1. That is, the touch force is calculated as above, andfourth control signal CN4 transmits this touch force information. Thedisplay panel 100 illustrated in FIGS. 1 and 2 may receive the fourthcontrol signal CN4 to convert it into an image such that informationdirected by the touch force F1 is displayed.

With a display device of the inventive concept, since sensing electrodesare formed of a piezoresistive material, it is possible to calculate atouch coordinate and a touch force applied by a user without a sensorfor measuring a force.

FIG. 8 is a cross-sectional view of a touch display device according toanother embodiment of the inventive concept. FIG. 9 is a top view of thetouch screen panel of FIG. 8. In FIG. 9, there is illustrated an examplein which a touch TCH is generated at a touch substrate SB by a user.Herein, the touch TCH may be generated to be overlapped with a 21stsensing electrode SE21 in a plane view, and a touch force F1corresponding to the touch TCH may be applied in a directionperpendicular to the touch screen SB.

Below, a touch display device 2000 according to another embodiment ofthe inventive concept will be described. The touch display device 2000may be the same or substantially the same as a touch display device 1000according to a previous embodiment of the inventive concept, except thatdriving electrodes DE are further included. Repetitive description ofcomponents that have already been described is omitted.

A touch screen panel 210 of the touch display device 2000 may include atouch substrate SB, sensing electrodes SE, driving electrodes DE,spacers SP, and a touch processor CP.

The sensing electrodes SE may be disposed on the touch substrate SB. Thesensing electrodes SE may be spaced apart from one another. In FIG. 9,there is illustrated an example in which sensing electrodes SE1 to SE60are arranged in a matrix of 4 rows and 10 columns.

The sensing electrodes SE1 to SE60 may be formed of a piezoresistivematerial having a resistance value that varies according to an appliedforce.

The driving electrodes DE may be disposed on the touch substrate SB. Thedriving electrodes DE may be spaced apart from one another. Capacitorsmay be formed between the sensing electrodes SE and the drivingelectrodes DE. In FIG. 9, there is illustrated an example in whichdriving electrodes DE1 to DE60 are arranged in a matrix of 4 rows and 10columns. That is, the number of the driving electrodes DE1 to DE60 maybe equal to that of the sensing electrodes SE1 to SE60, respectively.

A substantially constant voltage may be applied to the drivingelectrodes DE by the touch processor CP.

Referring to FIG. 9, an inherent capacitor may be formed between a 21stdriving electrode DE21 and a 21st sensing electrode SE21. If a touch TCHby a user is generated to be overlapped with the 21st sensing electrodeSE21, a touch capacitor may be formed between the user and the 21stsensing electrode SE21, and may be connected in parallel with theinherent capacitor. The combined capacitance of the touch and inherentcapacitors may be larger than that of the inherent capacitor. A sensingtime constant of a sensing signal SG21 provided to the 21st sensingelectrode SE21 may be larger than when the touch TCH is not generated.

FIG. 10 is a perspective view of a touch display device according tostill another embodiment of the inventive concept.

Below, a touch display device 3000 according to still another embodimentof the inventive concept will be described. The touch display device3000 may be the same or substantially the same as that in FIG. 8 or 9except for a touch substrate, sensing electrodes, and drivingelectrodes. In FIG. 10, a description on the remaining components exceptfor the touch substrate, sensing electrodes, and driving electrodes maybe omitted.

The touch screen panel 220 may include a first touch substrate SB1, asecond touch substrate SB2, sensing electrodes SE, driving electrodesDE, spacers SP1, and a touch processor.

The first touch substrate SB1 may be used to receive a touch of a user.The first touch substrate SB1 may be formed of a flexible material suchas plastic.

The first touch substrate SB1 may have a generally platelike shape. Asshown from a top, the first touch substrate SB1 may have a shapecorresponding to a shape of the display panel 100. In FIG. 10, there isillustrated an example in which a shape of the first touch substrate SB1is rectangular in plan view.

The second touch substrate SB2 may be formed to have a plate shapepositioned opposite to the first touch substrate SB1. The second touchsubstrate SB2 may be connected with an upper surface of the displaypanel 100.

If the second touch substrate SB2 is formed of an insulating material,its flexibility may not be limited. In other words, the second touchsubstrate SB2 may be formed of a flexible material or a nonflexiblematerial. Thus, the second touch substrate SB2 may be formed of plasticor glass.

The sensing electrodes SE may be disposed on the first touch substrateSB1. The sensing electrodes SE may be spaced apart from one another. Thesensing electrodes SE may be formed of a piezoresistive material havinga resistance value that varies according to an applied force.

The driving electrodes DE may be disposed on the second touch substrateSB2. The driving electrodes DE may be spaced apart from the sensingelectrodes SE, and capacitors may be formed between the drivingelectrodes DE and the sensing electrodes SE, respectively.

The driving electrodes DE and the sensing electrodes SE may not beoverlapped in plan view.

The spacers SP1 may be disposed between the first touch substrate SB1and the second touch substrate SB2. The spacers SP1 may be used tomaintain a cell gap between the first touch substrate SB1 and the secondtouch substrate SB2.

Heights of the spacers SP1 may be greater than those of the sensingelectrodes SE. Thus, the sensing electrodes SE may be spaced apart fromthe display panel 100 in a height direction. A space between the firsttouch substrate SB1 and the second touch substrate SB2 may be filled byair.

Below, still another embodiment of the inventive concept will bedescribed.

The touch display device 3000 may be the same or substantially the sameas that according to previous embodiments of the inventive conceptexcept for a touch processor. Below, a description on the remainingcomponents except for a processor may be omitted.

FIG. 11 is a diagram illustrating a touch processor according to stillanother embodiment of the inventive concept. FIG. 12 is a graphillustrating a division voltage according to a touch force.

Referring to FIGS. 11 and 12, a touch processor CP1 may sense a touchcoordinate and a touch force based on resistance values of sensingelectrodes SE illustrated in FIG. 3.

The touch processor CP1 may include an electrode resistor Rs, areference resistor Rf, a touch determining part 510, a coordinateextracting part 520, and a touch force calculating part 530.

The electrode resistor Rs may have the same resistance value as that ofeach of the sensing electrodes SE1 to SE60 in FIG. 3. In more detail,the electrode resistor Rs may be an equivalent resistor of the sensingelectrodes SE1 to SE60 seen from the touch processor CP1. That is,resistor Rs is an adjustable resistor whose resistance value is set tothe resistance value of the sensing electrode that is receiving thetouch force F1. The resistance value of the piezoresistive element isdetermined from the change in its sensing signal due to the touch, andRs is set accordingly.

Thus, a resistance value of the electrode resistor Rs may vary when aresistance value of the sensing electrodes SE1 to SE60 is varied by atouch force.

The reference resistor Rf may be connected in series with the electroderesistor Rs, and may have a constant resistance value.

The resistors Rf and Rs may be connected in series between a setupvoltage Vcc and a ground. One end of the reference resistor Rf may beconnected to a reference potential Vcc, one end of the electroderesistor Rs may be grounded, and the other ends of the resistors Rf andRs may be connected to each other.

The touch determining part 510 may be connected to a node ND between thereference resistor Rf and the electrode resistor Rs.

The touch determining part 510 may sense a division voltage Vd decidedby dividing the reference potential Vcc using the resistors Rf and Rs.The division voltage Vd may vary according to a variation in aresistance value of the electrode resistor Rs.

The division voltage Vd may be decided according to the above-describedequation 1.

The touch determining part 510 may determine a touch and a soft/hardtouch by comparing the division voltage Vd to a predetermined referencevoltage.

The reference voltage may include a first reference voltage V1 and asecond reference voltage V2. That the division voltage Vd is higher thanthe first reference voltage V1 may indicate that a touch is generated.In the case that the division voltage Vd is higher than the firstreference voltage V1 and lower than the second reference voltage V2, thetouch determining part 510 may determine the touch to be a soft touch.In the case that the division voltage Vd is higher than the secondreference voltage V2, the touch determining part 510 may determine thetouch to be a hard touch.

Returning to FIG. 11, when a touch is not generated, the touchdetermining part 510 may provide a first control signal SN1 to a displaypanel 100.

When a touch is generated, the touch determining part 510 may providethe coordinate extracting part 520 with a second control signal SN2including information associated with a soft/hard touch.

The coordinate extracting part 520 may extract the touch coordinate froma location of a sensing electrode corresponding to the division voltage.The coordinate extracting part 520 may provide the display panel 100with a third control signal SN3 including information associated withthe touch coordinate. The display panel 100 may receive the thirdcontrol signal CN3 to convert it into an image such that informationdirected by the touch coordinate is displayed. Also, when the touch is ahard touch, the coordinate extracting part 520 may provide the thirdcontrol signal SN3 to the touch force calculating part 530.

The touch force calculating part 530 may calculate the touch force F2based on the division voltage Vd.

For example, in the case that a force is not applied to a sensingelectrode, a resistance value of the electrode resistor Rs may beinfinite. In the case that an infinite force is applied to the sensingelectrode, a resistance value of the electrode resistor Rs may be zero.As a resistance value of the electrode resistor Rs varies, the divisionvoltage Vd may vary between 0V and Vcc.

The touch force calculating part 530 may include a lookup tableincluding force values respectively corresponding to voltage valuesbetween 0V and Vcc. The touch force calculating part 530 may read atouch force F2 corresponding to the division voltage Vd from the lookuptable. However, the inventive concept is not limited thereto. Forexample, the touch force calculating part 530 may be configured tocalculate the touch force F2 from the division voltage Vd using anappropriate coefficient.

The touch force calculating part 530 may provide the display panel 100with a fourth control signal SN4 having information associated with thetouch force. The display panel 100 may receive the fourth control signalSN4 to convert it into an image, such that information directed by thetouch force is displayed.

With a display device of still another embodiment of the inventiveconcept, a touch coordinate and a touch force associated with a touchmay be sensed using a division voltage based on a resistance value of asensing electrode, without need of information associated with a timeconstant of a signal applied to a sensing electrode. That is, the changein resistance of the piezoresistive sensing electrode due to touch forceis used to determine touch force, rather than time constant information.

While the inventive concept has been described with reference toexemplary embodiments, it will be apparent to those skilled in the artthat various changes and modifications may be made without departingfrom the spirit and scope of the present invention. Therefore, it shouldbe understood that the above embodiments are not limiting, butillustrative.

What is claimed is:
 1. A touch display device, comprising: a displaypanel configured for displaying an image; and a touch screen paneldisposed on the display panel and configured to detect at least onetouch, wherein the touch screen panel comprises: a touch substrate atwhich the touch can occur; sensing electrodes provided on the touchsubstrate and spaced apart from one another, each of the sensingelectrodes comprising a piezoresistive material having a resistance thatvaries according to a magnitude of an applied force; and a touchprocessor electrically connected to the sensing electrodes, the touchprocessor configured to determine a touch coordinate of the touch basedon time constants of sensing signals applied to the sensing electrodes,and configured to calculate a touch force of the touch based onresistance values of the sensing electrodes, and wherein the touchprocessor comprises: a touch determining part configured to determinethe presence of the touch, and whether the touch is soft touch or a hardtouch, by comparing the time constants to a predetermined reference timeconstant; and a coordinate extracting part configured to extract thetouch coordinate from locations of sensing electrodes corresponding tothe touch as determined based on the time constants.
 2. The touchdisplay device of claim 1, wherein the touch processor calculates thetouch coordinate and the touch force when the touch is a hard touch, andcalculates the touch coordinate when the touch is a soft touch.
 3. Thetouch display device of claim 2, wherein the piezoresistive material isSingle Walled Carbon Nanotube (SWNT), Multi Walled Carbon Nanotubes(MWNT), or graphene.
 4. The touch display device of claim 1, wherein thetouch substrate includes a flexible material.